This demonstration wedge is listed at 150 francs (about
$30) in the 1853 Lerebours et Secretan catalogue. It was proably bought
in the second half of the 1850s by Prof. Frederick Barnard of the University
of Mississippi, and is now on display at the University Museum

In use, the wedge was held with its vertex down, supported
by two rollers touching the outer surfaces sof the wedge. The rollers were
held in place by cords exerting vertical and horizontal forces. A weight
was suspended from the end of each cord, and a weight was attached to a
cord tied to the loop at the vertex.

The two weights pulling the rollers sideways against the
wedge were the same, and the two weights pulling upward on the rollers
added up to the sum of the weight of the wedge and the weight suspended
from its vertex. All of the numbers changed when the angle of the wedge
was adjusted.